Imaging device and manufacturing method thereof

ABSTRACT

An imaging device is provided, the imaging device including: a first-conductivity-type substrate; a first-conductivity-type element forming portion provided on the substrate, and having a concentration lower than the substrate; and a plurality of pixel portions provided in the element forming portion, and arrayed two-dimensionally, each pixel portion having a light receiving element, and a second-conductivity-type carrier absorbing portion provided in an area different from an area where the light receiving element is provided. At least one pixel portion of the pixel portions has: a first-conductivity-type first wall portion provided on a substrate side relative to the light receiving element, the first wall portion overlapping at least part of the light receiving element in an array direction of the pixel portions, and having a concentration higher than the substrate, and a carrier passage area not provided with the first wall portion in the array direction of the pixel portions.

This application is a continuation application of U.S. patentapplication Ser. No. 16/507,218, filed Jul. 10, 2019, which is in turn acontinuation of International Application PCT/JP2017/046792, filed Dec.26, 2017, and claims priority to Japanese Patent Application No.2017-014915, filed Jan. 30, 2017. The contents of these priorapplications are incorporated herein by reference in their entirety.

BACKGROUND 1. Technical Field

The present invention relates to an imaging device and an imaging devicemanufacturing method.

2. Related Art

There are conventional, known imaging devices having photodiodes (seePatent Literature 1, for example).

Patent Literature 1: Japanese Patent Application Publication No.2008-098601

However, in conventional imaging devices, dark current componentsgenerated in substrates are accumulated in photodiodes in some cases.

GENERAL DISCLOSURE

A first aspect of the present invention provides an imaging deviceincluding: a first-conductivity-type substrate; afirst-conductivity-type element forming portion that is provided on thesubstrate, and has a concentration lower than the substrate; and aplurality of pixel portions that are provided in the element formingportion, and are arrayed two-dimensionally, each pixel portion having alight receiving element, and a second-conductivity-type carrierabsorbing portion provided in an area different from an area where thelight receiving element is provided, wherein at least one pixel portionof the plurality of pixel portions has: a first-conductivity-type firstwall portion provided on the substrate side relative to the lightreceiving element, the first wall portion overlapping at least part ofthe light receiving element in an array direction of the plurality ofpixel portions, and having a concentration higher than the substrate,and a carrier passage area not provided with the first wall portion inthe array direction of the plurality of pixel portions.

A second aspect of the present invention provides an imaging devicemanufacturing method including: preparing a first-conductivity-typesubstrate; forming first-conductivity-type element forming portion onthe substrate, the element forming portion having a concentration lowerthan the substrate; forming a first-conductivity-type first wall portionand a carrier passage area in the substrate or the element formingportion, the first wall portion having a concentration higher than thesubstrate, the carrier passage area being not provided with the firstwall portion; and forming a light receiving element and asecond-conductivity-type carrier absorbing portion in the elementforming portion such that a plurality of pixel portions aretwo-dimensionally arrayed, the carrier absorbing portion being providedin an area different from an area where the light receiving element isprovided, each pixel portion having the light receiving element and thecarrier absorbing portion, wherein at least one pixel portion of theplurality of pixel portions includes the light receiving element formedto overlap at least part of the first wall portion in the arraydirection of the plurality of pixel portions.

The summary clause does not necessarily describe all necessary featuresof the embodiments of the present invention. The present invention mayalso be a sub-combination of the features described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an exemplary top view of an imaging device 100according to a first embodiment.

FIG. 1B illustrates an exemplary cross-sectional view taken along A-A′in the imaging device 100 according to the first embodiment.

FIG. 1C illustrates an exemplary cross-sectional view taken along B-B′in the imaging device 100 according to the first embodiment.

FIG. 2 illustrates a cross-sectional view of an imaging device 500according to a first comparative example.

FIG. 3 illustrates a cross-sectional view of the imaging device 500according to a second comparative example.

FIG. 4 illustrates a cross-sectional view of the imaging device 500according to a third comparative example.

FIG. 5 illustrates an exemplary configuration of the imaging device 100according to a second embodiment.

FIG. 6 illustrates an exemplary configuration of the imaging device 100according to a third embodiment.

FIG. 7A illustrates an exemplary step of forming first wall portions41a.

FIG. 7B illustrates an exemplary step of forming an element formingportion 20.

FIG. 7C illustrates an exemplary step of forming second wall portions42.

FIG. 7D illustrates an exemplary step of forming light receivingelements 32 and carrier absorbing portions 80.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, (some) embodiment(s) of the present invention will bedescribed. The embodiment(s) do(es) not limit the invention according tothe claims, and all the combinations of the features described in theembodiment(s) are not necessarily essential to means provided by aspectsof the invention.

First Embodiment

FIG. 1A illustrates an exemplary top view of an imaging device 100according to a first embodiment. FIG. 1B illustrates an exemplarycross-sectional view taken along A-A′ in the imaging device 100according to the first embodiment. FIG. 1C illustrates an exemplarycross-sectional view taken along B-B′ in the imaging device 100according to the first embodiment. The imaging device 100 of the presentexample includes a substrate 10, an element forming portion 20, pixelportions 30, a wiring layer 50, a color filter 60 and lens portions 70.The wiring layer 50 has wiring portions 55.

The substrate 10 is of a first conductivity type. The substrate 10 ofthe present example is a P type semiconductor substrate. Theconductivity type of the substrate 10 may be selected depending on thewavelength band of light that the imaging device 100 receives or thelike. For example, if the imaging device 100 receives light in theinfrared wavelength band, a P type substrate 10 is used. If thesubstrate 10 includes defects, carriers are generated from the substrate10 in some cases. Electrons are generated as carriers in the substrate10 of the present example. Carriers generated in the substrate 10 becomedark current components of the imaging device 100. Note that, inexplanations in the present specification, the first conductivity typeis P type, and a second conductivity type is N type. It should be notedhowever that similar principles apply even if the first conductivitytype is N type, and the second conductivity type is P type.

The element forming portion 20 is provided above the substrate 10. Theelement forming portion 20 is a P type semiconductor layer having aconcentration lower than the substrate 10. The element forming portion20 of the present example is an epitaxial layer or well layer formed onthe substrate 10. Note that, in the present specification, the Z-axispositive direction is defined as the upward direction, and the Z-axisnegative direction is defined as the downward direction. The plane onwhich the substrate 10 lies is defined as the X-Y plane perpendicular tothe Z axis.

Each pixel portion 30 receives light entering the imaging device 100.The imaging device 100 of the present example includes a plurality ofpixel portions 30 arrayed two-dimensionally. Each of the plurality ofpixel portions 30 has a light receiving element 32 and a carrierabsorbing portion 80. The plurality of pixel portions 30 are arrayed indirections parallel to the X axis and Y axis on the X-Y plane. In thepresent specification, the directions parallel to the X axis and Y axisare referred to as array directions of the pixel portions 30. At leastone pixel portion 30 of the plurality of pixel portions 30 has a firstwall portion 41.

Light receiving elements 32 are photodiodes that are arrayedtwo-dimensionally. The light receiving elements 32 of the presentexample have photodiodes PD1 and photodiodes PD2. The photodiodes PD1,and the photodiodes PD2 are arrayed in the X-axis direction. Aphotodiode PD1 and a photodiode PD2 are adjacent to each other in theY-axis direction.

Each first wall portion 41 suppresses accumulation, in a light receivingelement 32, of carriers generated in the substrate 10. In one example,the first wall portion 41 is a P type semiconductor layer having aconcentration higher than the substrate 10. The first wall portion 41 isprovided on the substrate 10 side relative to the light receivingelements 32. In addition, the first wall portion 41 is provided tooverlap at least part of a light receiving element 32 in the arraydirections of the plurality of pixel portions 30. That is, the firstwall portion 41 has a planar shape approximately parallel to the X-Yplane, and overlaps at least part of a light receiving element 32 in theplan view illustrated in FIG. 1A. The first wall portion 41 of thepresent example is provided in the substrate 10. The first wall portion41 is provided in the substrate 10 at its boundary with the elementforming portion 20. The first wall portion 41 may be formed to includethe boundary between the substrate 10 and the element forming portion20. In addition, the first wall portion 41 may be formed on thesubstrate 10 side in the element forming portion 20. It is optimal forthe first wall portion 41 to be provided at the boundary between them interms of restricting movement of carriers generated in the substrate 10toward the light receiving elements 32. Note that the first wall portion41 may be formed inside the element forming portion 20.

A carrier passage area Rcp refers to an area where carriers generated inthe substrate 10 pass. That is, the carrier passage area Rcp is aportion in the array directions of the plurality of pixel portions 30where the first wall portion 41 is not provided. The carrier passagearea Rcp overlaps at least part of a carrier absorbing portion 80 in thearray directions of the plurality of pixel portions 30.

Carrier absorbing portions 80 absorb carriers generated in the substrate10. The carrier absorbing portions 80 are provided in areas differentfrom the areas where the light receiving elements 32 are provided, inthe plan view. In the present specification, the plan view refers to aview as seen in the Z-axis direction. The carrier absorbing portions 80of the present example are N type impurity layers that absorb electronsgenerated in the substrate 10. For example, the carrier absorbingportions 80 are floating diffusion layers (floating diffusions: FD)formed in the pixel portions 30. It should be noted however that thecarrier absorbing portions 80 are not limited to them as long as theycan absorb carriers generated in the substrate 10.

For example, the carrier absorbing portions 80 include at least one of afloating diffusion (FD), the source or drain of a selection transistor(SEL), the source or drain of a reset transistor (RST), the source ordrain of an amplification transistor (SF), the source or drain of aswitch (TX1, TX2) interconnecting a plurality of floating diffusions,and a diffusion area of a power supply (VDD). Thereby, carriersgenerated in the substrate 10 pass through carrier passage areas Rcpbetween first wall portions 41, and are absorbed by the carrierabsorbing portions 80.

In one example, the carrier absorbing portions 80 are set at apredetermined potential. The carrier absorbing portions 80 arepreferably provided in electrically not floating areas. If the carrierabsorbing portions 80 are diffusion areas of a power supply, the carrierabsorbing portions 80 are fixed at the power supply voltage. Forexample, the carrier absorbing portions 80 are fixed at 5 V as the powersupply voltage.

Element isolating portions 22 cut off electrical connections betweenadjacent pixel portions 30. Thereby, the element isolating portions 22isolate adjacent pixel portions 30. The element isolating portions 22are provided on the upper end side in the element forming portion 20. Inaddition, the element isolating portions 22 are adjacent to carrierabsorbing portions 80 in the plan view. In one example, the elementisolating portions 22 are formed by STI (shallow trench isolation) inwhich trenches are formed in the element forming portion 20, and oxidefilms are embedded in the trenches.

The pixel portions 30 of the present example each include a first wallportion 41 and a carrier passage area Rcp. In addition, each pixelportion 30 has a carrier absorbing portion 80. Thereby, a pixel portion30 causes carriers generated in the substrate 10 to be absorbed by thecarrier absorbing portion 80 of the pixel portion 30. Dark currentcomponents are not accumulated in a light receiving element 32 of eachpixel portion 30. Therefore, noise resulting from dark currentdecreases, and the quality of an image captured by the imaging device100 improves.

Note that the pixel portions 30 may each share part of theirconfigurations with adjacent pixel portions 30. For example, a powersupply, a selection transistor, an amplification transistor, and a resettransistor may be shared among a plurality of adjacent pixel portions30. In the present example, two pixel portions 30 that are adjacent toeach other in the Y-axis direction share a power supply, a selectiontransistor, an amplification transistor, and a reset transistor. Thatis, two photodiodes, a photodiode PD1 and a photodiode PD2, are providedwith one power supply, one selection transistor, one amplificationtransistor, and one reset transistor.

The imaging device 100 of the present example guides carriers generatedin the substrate 10 to carrier absorbing portions 80 by using first wallportions 41. Thereby, the imaging device 100 suppresses accumulation, inlight receiving elements 32, of dark current components from thesubstrate 10. The imaging device 100 of the present example not onlysuppresses carriers generated in the substrate 10 at potential barriersformed by the first wall portions 41, but also guides the carriersthrough the carrier passage areas Rcp to the carrier absorbing portions80. That is, the first wall portions 41 also serve as guiding memberswhose function is to guide carriers to the carrier passage areas Rcp.Thus, as compared with the case where carriers are suppressed simply atthe potential barriers, the effect of suppressing dark currents ishigher.

FIRST COMPARATIVE EXAMPLE

FIG. 2 illustrates a cross-sectional view of an imaging device 500according to a first comparative example. The imaging device 500 of thepresent example includes a substrate 510, an element forming portion520, pixel portions 530, a wiring layer 550, color filters 560, and lensportions 570. The element forming portion 520 has light receivingelements 532, and floating diffusion layers 580 formed therein. Thewiring layer 550 has wiring portions 555.

The imaging device 500 has a P+ type substrate 510, and a P− typeelement forming portion 520. The substrate 510 includes defects in somecases. For example, if the substrate 510 includes defects, carriers aregenerated from the defects, and dark current is generated in some cases.If dark current is generated in the substrate 510, it flows into thelight receiving elements 532, and the characteristics of the imagingdevice 500 deteriorate.

SECOND COMPARATIVE EXAMPLE

FIG. 3 illustrates a cross-sectional view of the imaging device 500according to a second comparative example. The imaging device 500 of thepresent example is different from the imaging device 500 according tothe first comparative example in that the substrate 510 has a higherconcentration.

The imaging device 500 having the substrate 510 at a higher P typeimpurity concentration causes electrons generated in the substrate 510to recombine. Thereby, generation of dark current is suppressed.However, if the high concentration substrate 510 is used, it becomesdifficult to adjust the concentration of the element forming portion 520formed on the substrate 510. For example, if the element forming portion520 is to be formed on the substrate 510 by epitaxial growth, overdopingoccurs in which impurities of the substrate 510 are diffused in theelement forming portion 520.

THIRD COMPARATIVE EXAMPLE

FIG. 4 illustrates a cross-sectional view of the imaging device 500according to a third comparative example. The imaging device 500 of thepresent example is different from the imaging device 500 according tothe first comparative example in that it has a wall portion 541.

The wall portion 541 is a P type impurity layer provided over the entiresurface of the substrate 10. The wall portion 541 suppresses passage ofelectrons generated in the substrate 510 to the element forming portion520. However, the imaging device 500 of the present example does nothave an escape route for the electrons generated in the substrate 510 topass through. Thus, some of the electrons generated in the substrate 510pass through the wall portion 541 and enter the element forming portion520 in some cases. Therefore, although the imaging device 500 of thepresent example provides the effect of reducing dark current, it cannotsuppress dark current completely.

Note that there is a method of providing a cooling apparatus as apossible method of suppressing dark current in the imaging device 500.Generation of electrons in the substrate 510 is suppressed by coolingthe imaging device 500. However, the method of providing a coolingapparatus incurs significant disadvantages such as size increase or costincrease of an apparatus since the cooling apparatus is provided.Furthermore, since a method that involves cooling reduces thermaldiffusion of electrons, the characteristics of charge transfer from aphotodiode to a floating diffusion layer deteriorate.

Second Embodiment

FIG. 5 illustrates an exemplary configuration of the imaging device 100according to a second embodiment. The imaging device 100 of the presentexample is different from the imaging device 100 according to the firstembodiment in that it includes second wall portions 42. In the presentexample, differences from the first embodiment are explained mainly.

The second wall portions 42 suppress accumulation, in the lightreceiving elements 32, of carriers having passed through the carrierpassage areas Rcp. That is, the second wall portions 42 are provided toguide the carriers having passed through the carrier passage areas Rcpto the carrier absorbing portions 80. The second wall portions 42 extendinclined to the array directions of the plurality of pixel portions 30,and are provided in the element forming portion 20. The second wallportions 42 of the present example have tabular shapes, and have theirsurface directions along the Z-axis direction. The second wall portions42 are P type semiconductor layers having a concentration higher thanthe element forming portion 20. The second wall portions 42 arepreferably formed in contact with the first wall portions 41.

In one example, the second wall portions 42 are provided in contact withthe element isolating portions 22. In this case, the positions of theupper ends of the second wall portions 42 may be positioned on the upperend side in the element forming portion 20 relative to the positions ofthe lower ends of the carrier absorbing portions 80. The second wallportions 42 of the present example are provided below the elementisolating portions 22. Thereby, the second wall portions 42 preventcarriers generated in the substrate 10 from not being absorbed by thecarrier absorbing portions 80 and so from being accumulated in the lightreceiving elements 32. The positions at which the second wall portions42 are provided are not limited to these positions as long as they canguide the carriers generated in the substrate 10 to the carrierabsorbing portions 80. For example, the second wall portions 42 may haveinclined surface directions as long as they extend inclined to the arraydirections of the plurality of pixel portions 30. Specifically, thesecond wall portions 42 may be inclined such that the second wallportions 42 become closer to the carrier absorbing portions 80 in theplan view at higher portions thereof. By providing the second wallportions 42 such that the areas from the carrier passage areas Rcp tothe carrier absorbing portions 80 dwindle gradually, it becomes easierfor carriers generated in the substrate 10 to be guided to the carrierabsorbing portions 80. Note that the second wall portions 42 are notnecessarily required to be tabular, but may have stepwise shapes orcurved shapes, for example.

The impurity concentration of the second wall portions 42 is the same asthe impurity concentration of the first wall portions 41, in oneexample. It should be noted however that the impurity concentration ofthe second wall portions 42 may be different from the impurityconcentration of the second wall portions 42. In one example, theimpurity concentration of the first wall portions 41 is higher than theimpurity concentration of the second wall portions 42. The impurityconcentrations of the first wall portions 41 and second wall portions 42may result from ion implantation at the same dopant concentration. Ifthe first wall portions 41 are formed in the high concentrationsubstrate 10, and the second wall portions 42 are formed in the elementforming portion 20 having a concentration lower than the substrate 10,the impurity concentration of the first wall portions 41 becomes higherthan the impurity concentration of the second wall portions 42 even ifions are implanted at the same dopant concentration.

Third Embodiment

FIG. 6 illustrates an exemplary configuration of the imaging device 100according to a third embodiment. The imaging device 100 of the presentexample has a plurality of stacked first wall portions 41 a, 41 b, 41 c.

Similar to the first wall portions 41 according to the first and secondembodiments, each first wall portion 41 a is formed at the upper surfaceof the substrate 10. The first wall portion 41 a of the present exampleis provided to cover the entire surface of a light receiving element 32in the plan view.

Each first wall portion 41 b is provided below a first wall portion 41a. The first wall portion 41 b is provided in an area of a lightreceiving element 32 corresponding to its center side in the plan view.In addition, the first wall portion 41 b is provided in an area smallerthan the first wall portion 41 a in the plan view. The impurityconcentration of the first wall portions 41 b is the same as theimpurity concentration of the first wall portions 41 a. It should benoted however that the impurity concentration of the first wall portion41 b may be different from the impurity concentration of the first wallportion 41 a.

Each first wall portion 41 c is provided below a first wall portion 41a. The first wall portion 41 c is provided below a first wall portion 41b. The first wall portion 41 c is provided in an area of a lightreceiving element 32 corresponding to its center side in the plan view.In addition, the first wall portion 41 c is provided in an area smallerthan the first wall portion 41 a and first wall portion 41 b in the planview. That is, the plurality of first wall portions 41 a, 41 b, 41 c areprovided to have areas that decrease in width in the order from the onecloser to the light receiving element 32 to the one closer to thesubstrate 10. The impurity concentration of the first wall portions 41 cis the same as the impurity concentrations of the first wall portions 41a and first wall portion 41 b. It should be noted however that theimpurity concentration of the first wall portion 41 c may be differentfrom the impurity concentrations of the first wall portion 41 a andfirst wall portion 41 b.

The electron potential distribution in the Z-axis direction becomes highnear the first wall portions 41 a. The first wall portions 41 of thepresent example include the first wall portions 41 a, the first wallportions 41 b and the first wall portions 41 c that are formed in thisorder from the Z-axis positive side. The areas where the first wallportions 41 a are formed are larger than the areas where the first wallportions 41 b are formed. In addition, the areas where the first wallportions 41 b are formed are larger than the areas where the first wallportions 41 c are formed. Thus, the electron potential distribution inthe Z-axis direction is inclined such that the potential is high at thedepth position of the first wall portions 41 a, and is low at the depthpositions of the first wall portions 41 b and first wall portions 41 c.Therefore, it becomes easier for electrons formed in the substrate 10 tobe guided downward from the first wall portion 41 a side. Accordingly,the effect of suppressing accumulation of electrons in the lightreceiving element 32 as a result of the electrons moving past the firstwall portions 41 a becomes higher.

On the other hand, their areas in the X-axis direction increase in theorder from the one located lower to the one located higher, that is, inthe order of the first wall portions 41 c, 41 b, and 41. Thereby, theareas with high potential in the X-axis direction increase in the orderfrom the one located lower to the one located higher, that is, in theorder of the first wall portions 41 c, 41 b, and 41 a. Therefore, itbecomes easier for electrons formed in the substrate 10 to be guided tothe carrier passage areas Rcp as they advance from lower regions tohigher regions.

FIG. 7A to FIG. 7D illustrate an exemplary method of manufacturing theimaging device 100. The manufacturing method of the present example ismerely one example, and the imaging device 100 may be manufactured by adifferent method.

FIG. 7A illustrates an exemplary step of forming the first wall portions41. First, the P type substrate 10 is prepared. The first wall portions41 are formed by ion implantation onto the front surface of thesubstrate 10. The first wall portions 41 of the present example areformed to have an impurity concentration higher than the impurityconcentration of the substrate 10 by performing ion implantation of a Ptype dopant. In this manner, the step of forming the first wall portions41 of the present example is executed before a step of forming theelement forming portion 20 above the substrate 10. Thereby, the firstwall portions 41 are formed at the upper surface of the substrate 10. Inaddition, by performing ion implantation before formation of the elementforming portion 20, the first wall portions 41 can be formed with asmall acceleration energy.

FIG. 7B illustrates an exemplary step of forming the element formingportion 20. The P type element forming portion 20 having a concentrationlower than the substrate 10 is formed above the substrate 10. Theelement forming portion of the present example 20 is formed by epitaxialgrowth on the substrate 10. In addition, after the formation of theelement forming portion 20, a well layer for forming a peripheralcircuit may be formed. Note that if the first wall portions 41 areformed not in the substrate 10 but in the element forming portion 20,the element forming portion 20 may be formed without performing theformation of the first wall portions 41 illustrated in FIG. 7A, and thenthe first wall portions 41 may be formed by performing ion implantationof a P type dopant in the element forming portion 20. In addition, thefirst wall portions 41 may be formed, and then the element formingportion 20 may be further formed above the first wall portions 41.

FIG. 7C illustrates an exemplary step of forming the second wallportions 42. A step of forming the second wall portions 42 in theelement forming portion 20 may further be provided after the step offorming the element forming portion 20 above the substrate 10. Forexample, the second wall portions 42 of the present example are formedat once after completely forming the element forming portion 20. Thesecond wall portions 42 of the present example are formed by performingion implantation of a P type dopant from above the element formingportion 20.

In addition, a step of forming the second wall portions 42 in theelement forming portion 20 may be provided before the step of completelyforming the element forming portion 20 above the substrate 10. In thiscase, the formation of the element forming portion 20 and the formationof the second wall portions 42 may be performed at multiple separatesteps. For example, the second wall portions 42 are formed by repeating,multiple times, the step of forming the element forming portion 20 abovethe substrate 10, and the step of forming the second wall portions 42 inthe element forming portion 20. Here, in some cases, the accelerationenergy of the ion implantation for the second wall portions 42 islimited, and the ion implantation for the element forming portion 20cannot be performed at once. Even in such a case, the formation of thesecond wall portions 42 is realized by performing the ion implantationinto the element forming portion 20 at separate multiple steps.

FIG. 7D illustrates an exemplary step of forming the light receivingelements 32 and carrier absorbing portions 80. The light receivingelements 32 and carrier absorbing portions 80 may be formed in theelement forming portion 20 by typical semiconductor processes.

The light receiving elements 32 are formed corresponding to the firstwall portions 41. In one example, the light receiving elements 32 areformed to at least partially overlap the first wall portions 41 in theplan view. In addition, the entire areas of the light receiving elements32 may be formed to overlap the first wall portions 41 in the plan view.The light receiving elements 32 are formed on the front surface side inthe element forming portion 20. The first wall portions 41 of thepresent example are formed on the substrate 10 side relative to thelight receiving elements 32 such that the first wall portions 41 overlapat least parts of the light receiving elements 32 in the arraydirections of the plurality of pixel portions 30.

The carrier absorbing portions 80 are formed corresponding to thecarrier passage areas Rcp. In one example, the carrier absorbingportions 80 are formed to at least partially overlap the carrier passageareas Rcp in the plan view. In addition, the entire areas of the carrierabsorbing portions 80 may be formed to overlap the carrier passage areasRcp in the plan view. Note that after the light receiving elements 32and carrier absorbing portions 80 are formed, the wiring layer 50, colorfilters 60, and lens portions 70 are formed at typical steps.

While the embodiments of the present invention have been described, thetechnical scope of the invention is not limited to the above describedembodiments. It is apparent to persons skilled in the art that variousalterations and improvements can be added to the above-describedembodiments. It is also apparent from the scope of the claims that theembodiments added with such alterations or improvements can be includedin the technical scope of the invention.

The operations, procedures, steps, and stages of each process performedby an apparatus, system, program, and method shown in the claims,embodiments, or diagrams can be performed in any order as long as theorder is not indicated by “prior to,” “before,” or the like and as longas the output from a previous process is not used in a later process.Even if the process flow is described using phrases such as “first” or“next” in the claims, embodiments, or diagrams, it does not necessarilymean that the process must be performed in this order.

EXPLANATION OF REFERENCE SYMBOLS

10: substrate; 20: element forming portion; 22: element isolatingportion; 30: pixel portion; 32: light receiving element; 41: first wallportion; 42: second wall portion; 50: wiring layer; 55: wiring portion;60: color filter; 70: lens portion; 80: carrier absorbing portion; 100:imaging device; 500: imaging device; 510: substrate; 520: elementforming portion; 530: pixel portion; 532: light receiving element; 541:wall portion; 550: wiring layer; 555: wiring portion; 560: color filter;570: lens portion; 580: floating diffusion layer

What is claimed is:
 1. An imaging device comprising: afirst-conductivity-type substrate; a first-conductivity-type elementforming portion that is provided on the substrate, and has aconcentration lower than the substrate; and a plurality of pixelportions that are provided in the element forming portion, and arearrayed two-dimensionally, each pixel portion having a light receivingelement, and a second-conductivity-type carrier absorbing portionprovided in an area different from an area where the light receivingelement is provided, wherein at least one pixel portion of the pluralityof pixel portions has: a first-conductivity-type first wall portionprovided on a substrate side relative to the light receiving element,the first wall portion overlapping at least part of the light receivingelement in an array direction of the plurality of pixel portions, andhaving a concentration higher than the substrate, and a carrier passagearea not provided with the first wall portion in the array direction ofthe plurality of pixel portions.
 2. The imaging device according toclaim 1, wherein the carrier passage area overlaps at least part of thecarrier absorbing portion in the array direction of the plurality ofpixel portions.
 3. The imaging device according to claim 1, wherein thefirst wall portion is provided in the substrate.
 4. The imaging deviceaccording to claim 3, wherein the first wall portion is provided in thesubstrate at a boundary thereof with the element forming portion.
 5. Theimaging device according to claim 1, further comprising a second wallportion that is provided in the element forming portion, extendsinclined to the array direction of the plurality of pixel portions, andhas a concentration higher than the element forming portion.
 6. Theimaging device according to claim 5, wherein one end of the second wallportion is positioned opposite to the substrate relative to a positionof an end of the carrier absorbing portion closer to the substrate. 7.The imaging device according to claim 5, further comprising an elementisolating portion that is provided on a side in the element formingportion opposite to the substrate, and is provided adjacent to thecarrier absorbing portion in a plan view, wherein the second wallportion is provided in contact with the element isolating portion. 8.The imaging device according to claim 5, wherein the concentration ofthe first wall portion is higher than the concentration of the secondwall portion.
 9. The imaging device according to claim 1, wherein aplurality of the first wall portions are provided, the plurality offirst wall portions being stacked one on another, and the plurality offirst wall portions have areas that decrease in width as a distance fromthe light receiving element toward the substrate increases.
 10. Theimaging device according to claim 1, wherein the carrier absorbingportion includes at least one of a floating diffusion, a source or drainof a selection transistor, a source or drain of a reset transistor, asource or drain of an amplification transistor, a source or drain of aswitch interconnecting a plurality of floating diffusions, and adiffusion area of a power supply.
 11. The imaging device according toclaim 1, wherein the carrier absorbing portion is set to a predeterminedpotential.
 12. An imaging device comprising: a substrate; an elementforming portion provided on the substrate; and a plurality of pixelportions that are arrayed two-dimensionally in at least one of thesubstrate and the element forming portion, each pixel portion having alight receiving element, wherein at least one pixel portion of theplurality of pixel portions has a first wall portion provided on asubstrate side relative to the light receiving element, the first wallportion overlapping at least part of the light receiving element in thearray direction of the plurality of pixel portions, and having aconcentration higher than the substrate.
 13. The imaging deviceaccording to claim 12, wherein the plurality of pixel portions each havea carrier absorbing portion provided in an area different from an areawhere the light receiving element is provided, the at least one pixelportion has a carrier passage area not provided with the first wallportion in the array direction of the plurality of pixel portions, andthe carrier passage area is provided to overlap at least part of thecarrier absorbing portion in the array direction of the plurality ofpixel portions.
 14. The imaging device according to claim 13, whereinthe substrate and the element forming portion are of the sameconductivity type, the element forming portion has a concentration lowerthan the substrate, and the carrier absorbing portion is of aconductivity type different from the conductivity type of the substrateand the element forming portion.
 15. An imaging device manufacturingmethod comprising: preparing a first-conductivity-type substrate;forming a first-conductivity-type element forming portion on thesubstrate, the element forming portion having a concentration lower thanthe substrate; forming a first-conductivity-type first wall portion anda carrier passage area in the substrate or the element forming portion,the first wall portion having a concentration higher than the substrate,the carrier passage area being not provided with the first wall portion;and forming a light receiving element and a second-conductivity-typecarrier absorbing portion in the element forming portion such that aplurality of pixel portions are two-dimensionally arrayed, the carrierabsorbing portion being provided in an area different from an area wherethe light receiving element is provided, each pixel portion having thelight receiving element and the carrier absorbing portion, wherein atleast one pixel portion of the plurality of pixel portions includes thelight receiving element formed to overlap at least part of the firstwall portion in the array direction of the plurality of pixel portions.16. The imaging device manufacturing method according to claim 15,further comprising, after forming the element forming portion on thesubstrate, forming a second wall portion in the element forming portion,the second wall portion having a concentration higher than thesubstrate.
 17. The imaging device manufacturing method according toclaim 16, comprising repeating multiple times: forming the elementforming portion on the substrate; and forming the second wall portion inthe element forming portion.
 18. An imaging device manufacturing methodcomprising: preparing a substrate; forming an element forming portion onthe substrate; forming a first wall portion in at least one of thesubstrate and the element forming portion, the first wall portion havinga concentration higher than the substrate; and two-dimensionallyarraying a plurality of pixel portions in the element forming portion,each pixel portion having a light receiving element, wherein at leastone pixel portion of the plurality of pixel portions has the lightreceiving element formed to overlap at least part of the first wallportion in the array direction of the plurality of pixel portions.